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Heart Sounds

S1 – It is produced primarily by closure of AV valve.
  1. Loud S1  (Causes):  Mitral stenosis, Tricuspid stenosis, Tachycardia, Short PR interval
    ASD (Increase AV flow in L → R & increase AV flow in hyperkinetic state)         
  2. Soft S1 (Causes): Mitral valve calcification, MR, TR, Obesity, Prolonged PR interval , Left  pleural effusion, obesity.
  3. S1 split is seen in Ebstein anomaly, RBBB 

Important Points:

  1. S1 is of Lower frequency than S2
  2. S1 is cause by closure of mitral valve
  3. S1 is soft in Left pleural effusion, obesity because of poor conduction of sound through chest wall.
  4. S1 is Loud due to.
    1. Prolonged flow through mitral vale
    2. Short PR interval.

S2 – Due to closure of aortic (A2) and pulmonary (P2) valves.

  1. Single S2 TOF, Truncus Arterious, Pulmonary Atresia, Tricuspid Atresia, Eisenmenger syndrome, Severe PS
  2. Soft S2
    1. Calcific aortic valve
    2. Calcific pulmonary stenosis
  3. Loud A2  Systemic hypertension
  4. Loud P2  Pulmonary HT
  5. S2 splitting Normal (A2 – P2 ) interval 30 ms
  6. Wide variable splitting of S2 –RBBB, PS
  7. Wide fixed splitting of S2 – Atrial septal defect.
  8. Reverse/ Paradoxical splitting of S2P2 Precede A2
  9. Splitting is maximal in expiration and decrease during inspiration – LBBB, AS, WPW (Type B)

Important Points: WPW syndrome type A and LV pacing are not associated with reversed splitting. WPW syndrome type B and RV pacing are associated with reversed splitting.


S3 – Produced by initial rapid filling phase of the ventricles in diastole.


(Ventricular gallop) – Low pitch sound.                                                     


  1. Physiological: Children, Athlete, Pregnancy
  2. Pathological: High output states, MR,AR,TR, CAD,  CHF, Thyrotoxicosis, fever.
  3. S3 which is earlier, i.e. 100 – 120 m sec after A2 and higher pitch and is called pericardial knock seen in constrictive pericarditis 


  1. Also known as presystolic or atrial gallop.
  2. It is never physiological
  3. It is produced by emptying of the atrium into non compliant ventricle.
  4. It is associated with effective atrial contraction and hence absent in patients with atrial fibrillation’s
  5. Causes Systemic, HTn Q , AS Q ,HOCM, CAD, acute MR, delay in Av conduction (Ref. Hari. 18th ed., pg -1826) 
(Extra Edge: It is not seen in LV aneurysm)
Important Points:
  1. Incidence of S4 increase with age
  2. Incidence of S3 decrease with age
  3. S3, S4 is low pitched sound & heard best with bell of stetho.
  4. Summation gallop: The combined presence of S3 and S4 is a quadruple gallop. At rapid heart rates, S3 and S4 may merge to produce a summation gallop.
OS (Opening snap) –
  1. High pitch, due to opening of AV valve.
  2. It indicates that valve is pliable and it is not calcified. Q                                
  3. Causes – MS, TS 

Ejection clicks

  1. Produced by opening of semilunar valve.    
  2. It is high pitch sound.
  3. Causes -AS (valvular), PS (valvular) 

Important Points: OS & ejection click are high pitched & are heard best with diaphragm of stetho scope.


Important Points:

  1. Diastolic sounds:
    1. Opening Snap
    2. S3
    3. S4
    4. Pericardial knock
    5. Tumor plop.
  2. Systolic sound -
    1. Ejection click

Extra Edge: Tumour plop & opening snap are early diastolic sound.

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